PARALLEL_IO_CAP_ENABLED

Property

Description

Parameter type

Boolean

Default value

false

Modifiable

ALTER SESSION, ALTER SYSTEM

Range of values

true | false

Basic

No

Real Application Clusters

Multiple instances can have different values.

PARALLEL_IO_CAP_ENABLED specifies whether or not Oracle caps the default degree of parallelism to no greater than what the I/O system can support. This new value is calculated based on the results of the resource manager's I/O calibration package.

If PARALLEL_IO_CAP_ENABLED is set to true and the database I/O capacity has been calibrated, then Oracle will reduce the default degree of parallelism if the I/O capacity cannot support the available number of CPUs. To calibrate the I/O capacity, use the DBMS_RESOURCE_MANAGER.CALIBRATE_IO procedure to measure the system's I/O capacity. Oracle then computes the degree of parallelism so as not to exceed the system's I/O capacity.